Improvement in the manufacture of paper-pulp from straw



UNITED STATES PATENT OFFICE.

CHARLES M. ORESSON, OF ,PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO ROBERTP. DEOHERT, OF SAME PLACE.

IMPROVEMENT IN THE MANUFACTURE OF PAPER-PULP FROM STRAW.

Specification forming part of Letters Patent No. 116,933, dated July 11,1871.

To all whom it may concern:

Be it known that I, CHARLES M. GnEssoN, M. D., of the city ofPhiladelphia and State of Pennsylvania, have made an invention ofImproved Processes for the Manufacture of Paper- Pulp from Straw; and Inow declare the following to be a true and accurate description of thesaid invention. v

The object of the invention is to produce a fibrous mass from strawwhich shall be capable of being felted and formed into sheets and suitedfor paper making, and, when desired to be of a white color, to be easilybleached; the production of such a pulp to be accomplished with theleast expenditure of time, labor, fuel, alkali, and bleach, the processbeing capable of such modifications as will admit of the relativeadaptation or proportioning of these expenditures so as to suit thechanges of the market value of each element, from time to time, and thusto secure the most economical results. The invention consists in thecombined use of a water-bath in an open vessel, or under pressure,together with boiling in caustic or carbonated alkaline solutions,either under pressure or in an open vessel, as hereinafter described;bleach to be used with the product when desired.

By experiment I have ascertained that, byboiling straw in ordinarysoft-water, we can extract a certain amount of its substance, amounting1n some instances to more than seventy per cent. of its weight, theamount depending upon the volume of water used and upon the duration ofthe boiling and the temperature to which the solution is subjected. Thestraw, when subjected to the treatment of boiling in a moderate amountof water and at not too high a temperature, loses its bright color andcharacteristic rigidity, and becomes changed into a soft and pliantmaterial which will easily split into filaments, but which will notwithout further chemical treatment be converted into suitable pulp oreasily whiten by the application of bleach, and is not fit to be formedinto white paper. If this boiling in water is made at too high atemperature the straw will be broken up into a fibrous mass of darkcolor, which cannot be converted into a pulp fit for white paper bymeans of subsequent treatment with a moderate percentage of alkali orbleach. I have also found that the matter extracted from straw byboiling in water has acid reactions, and

that it will neutralize a considerable amount of alkali. I have alsofound that the acid solution produced is capable of dissolving portionsof the intercellular matter of the straw which are not so readilydissolved either in water or solutions of caustic or carbonated alkali.I have further found that, by treating straw with a proper amount ofwater for a longer time at a low temperature, or for a shorter time at ahigh temperature, we are enabled to produce a good pulp by boiling theresultant product in a solution containing a much less percentageofcaustic or carbonated alkali than is necessary when the straw istreated only by caustic-alkali solution s, and at a lower temperaturethan by any other means known to me, and that the said pulp will whitenwith less percentage of bleach than any pulp produced at similartemperatures, and by the use of an equal percentage of alkali.Furthermore, I have found that by the combined use of a water treatmentat a hightemperature, and the use of an alkaline bath of much less percentage of caustic alkali than is now employed, also at a hightemperature, a pulp is produced from straw that will whiten with a lesspercent age of bleach than that produced by any process now known to me;and that by properly proportioning the amount of water used, and thepressure, and the percentage of caustic or carbonated alkali used, andthe temperature, we can obtain from straw a greater percentage of pulplit for making good white paper than can be obtained by any otherprocess or processes that I have a knowledge of.

I take any given amount of straw and (after washing it and cutting itinto short pieces, or not, at pleasure) place it in a boiler with fromsix to nine times its weight of water say seventy to one hundred and tengallons of water to one hundred pounds of strawand boil it from two toten hours in an open boiler, (keeping up the supply of water as lost byevaporation, .or from thirty minutes to three hours in aclosed boiler,at any temperature that is convenient, say from zero to one hundred andfifty pounds per square inch. The temperature and volume of water andtime of boiling determine the amount of alkali and the temperaturenecessary for the second part of the process, and greatly influence thepercentage of pulp obtainable. tractive matter (within the limitshereinafter in- The less the amount of exdicated) removed by the water,the greater is the amount of alkali and temperature necessary to producea pulp that will whiten with a given percentage of bleach. I do notlimit myself to the exact amount of water as herein expressed in whichthe straw is to be boiled; for, in order to produce the most economicalresults, it is necessary to adapt it to the age and condition of thestraw to be treated. In the operation with an open vessel, water enoughshould be used to re move from twelve to twenty per cent. of thesubstance of the straw. For the production of a finer pulp, and when theboiling in water is under pressure, the volume of water and temperatureshould be so proportioned as to remove from twenty to forty per cent. ofthe substance of the straw. The volume of water to be enr ployed, asbefore specified, I have foun d suitable for use with good dry wheat andrye straw from six to twelve months old, and from which the knots havenot been removed. If the boiling in water is carried on in such a manneras to remove more than forty-five per cent. of the substance of thestraw the percentage of the pulp obtained will be very much diminished,and without a corresponding useful diminution of the alkali necessaryfor the second part of the treatment, or of the bleach necessary towhiten the pulp. And if the boiling be carried on with such a volume ofwater, and at such a high temperature as to break up the structure ofthe straw and to reduce it to filaments or fibers, it will be found thatthe result cannot be easily converted into a pulp fit for white paper bysubsequent treatment with alkali or bleach, or both combined. I findthat the best results can be obtained by the employment of fromfifty-five to eighty pounds to the square inch, as a high pressure foreither the first or second part of the treatment, and that the onlyadvantage in using a higher pressure is to shorten the time of treatmentnecessary, and that, as a general rule, the use of such higher pressuresentail a percentage of loss by the mechanical detaclnnent and separation of the more minute vessels in the pulp, so that they pass off inthe water employed to cleanse the pulp in subsequent stages of itspreparation. I have found that, by boiling straw in an open vessel forten hours with nine times its weight of water, I could, by boiling theresult in a solution of caustic soda (NaO) containing of caustic soda anamount equal to fourteen per cent. of the weight of the straw, produce apulp at forty-five pounds pressure (about 300 Fahrenheit) that wouldwhiten with less than twenty. per cent. of its weight of bleach; andthat, by boiling straw in seven times its weight of water, at a pressureof one hundred to one hundred and twenty pounds per square inch, forhalf an horn to an hour, and again boiling the result in a solution ofcaustic soda (NaO) containing of caustic soda an amount equal to elevenper cent. of the weight of the straw, for two hours, at a pressure ofseventy pounds, I could produce a pulp that would whiten with less thantwelve per cent. of its weight of bleach. The straw is best prepared bycutting into small pieces and washing it, al-

though neither operation is absolutely necessary. It is then to besubjected to the process of boiling in water, as before described,either in an open vessel, or under pressure; the water is then to bedrawn off or blown off, and while the material is still hot the alkalinesolution is to be run on, and the second part of the treatment gone onwith.

I h.ve allowed the resultant material from the waterboiled to becomedrybetween the stages of the process, but it is much better not to doso. As soon as the material is sufficiently boiled in the alkalinesolution it can be treated by any preferred mode for disintegrating,screening, washing, and bleaching. By boiling straw in the larger volumeof water and at a high pressure (over fiftyfive pounds) we obtain aresult which, if treated with a solution of caustic alkali containing ofcaustic soda (NaO) an amount equal to ten or twelve per cent. of theoriginal weight of straw, also at a high pressure, we obtain a moderatepercentage of pulp which will readily whiten with a small amount ofbleach, and will make a soft and fine white paper. By boiling st aw withabout seven times its weight of water at a pressure of sixty to eightypounds to the square inch, from thirty minutes to an hour, and blowingout the solution, and then boiling the resultant product in a solutionof caustic alkali containing of caustic soda (NaO) an amount equal toten or twelve per cent. of the original weight of straw, at a pressureof forty-five to fifty pounds to the square inch, we obtain a largerpercentage of pulp, and one that will whiten readily with a moderateamount of bleach.

To produce a pulp from which an ordinary paper can be made one notrequired to be of a pure white C0101l13l$ only necessary to make theboiling in water in a large volume of water, and in an open. vessel, andto boil the result in a caustic alkaline solution, at any pressure aboveatmospheric pressure, (the less the pressure the greater percentage ofpulp obtained,) or to boil the straw in a smaller volume of water, atany pressure above atmospheric pressure, (212 Fahrenheit,) and then toboil the result in a solution of caustic alkali, in an open vessel.

To produce a pulp that will make a fine and soft white paper from strawalone requires that both boilings be made under pressure, and, if bothbe made at a pressure giving a temperature above 310 Fahrenheit, aminimum of alkali and bleach will be required; but, at temperaturesabove 310 Fahrenheit, the yield of pulp diminishes considerably, andsuch temperatures should only be used when great economy of time and ofbleach is necessary, and a very soft white paper is desired.

I find it useful to run or blow the acid liquor (obtained by boiling thestraw in water) through the straw that is about to be subjected to theprocess of boiling in water, and that it is useful, after having blownoff the acid liquor, to blow or run the waste alkaline solution over theresult, (obtained from the straw by boiling it in water,) to insure theremoval or neutralization of the acid extract, which would otherwiseneutralize and render inefficient a portion of the alkali employed inthe second part of the process. The waste solution retains sufficientalkaline properties to neutralize the acid solutions remaining in theinterstices of the material about to be subjected to a boiling in analkaline solution. In the treatment in an open vessel the boiling may beby means of a fire beneath it or by steampipes or jackets, or by jets ofsteam blown into or through the liquid in which the straw or materialhas been immersed.

I do not here claim the use of the solution produced by boiling straw inwater for breaking down a second batch of straw, as it will form thesubject of another application for Letters Patent; but

Witnesses:

HENRY LEFFMAN, M. D., WM. A. STEEL.

